Displays With Optical Edge Sensors

ABSTRACT

A display may have an array of light-emitting pixels that display an image in an active area of the display. These light-emitting pixels may be visible light pixels such as red, green, and blue thin-film organic light-emitting diode pixels. The display may also have a border region that runs along a peripheral edge of the active area. The border region may be free of pixels that display image light, whereas the active area may be free of light detectors. A non-optical touch sensor such as a capacitive touch sensor may overlap the active area to gather touch input from the active area. The non-optical touch sensor may not overlap any portion of the border region. In the border region, an optical sensor formed from infrared light-emitting pixels and infrared light-sensing pixels or other optical sensing circuitry may serve as an optical touch sensor.

This application claims the benefit of provisional patent applicationNo. 62/906,590, filed Sep. 26, 2019, which is hereby incorporated byreference herein in its entirety.

BACKGROUND

This relates generally to electronic devices and, more particularly, toelectronic devices with displays.

Electronic devices often include displays. For example, cellulartelephones have displays for presenting information to users. Displaysare often provided with capacitive touch sensors for gathering touchinput. The incorporation of a capacitive touch sensor into a displayallows a user to control device operation using touch input, but maypresent integration challenges for some cellular telephones.

SUMMARY

A display may have an array of light-emitting pixels that display animage in an active area of the display. These light-emitting pixels maybe visible light pixels such as red, green, and blue thin-film organiclight-emitting diode pixels. During operation of an electronic devicethat contains the display, the display may be used in presenting visualcontent for the user in the active area.

The display may also have a border region that runs along a peripheraledge of the active area. The border region is free of pixels thatdisplay image light. A non-optical touch sensor such as a capacitivetouch sensor may overlap the active area to gather touch input from theactive area. The non-optical touch sensor may not overlap any portion ofthe border region.

To gather touch input or other user input in the border region theborder region may have an optical sensor. For example, an optical sensorin the border region may be formed from infrared light-emitting pixelsand infrared light-sensing pixels. The optical sensing circuitry of theborder region may serve as an optical touch sensor. By gathering touchinput in the border region using the optical sensor in the border regionand by gathering touch input in the active area using the non-opticaltouch sensor, most or all of the area covering the display may beresponsive to user touch input.

The optical sensor may have light-sensing pixels and light-emittingpixels that share common signal lines or the light-sensing pixels mayuse a first signal line while the light-emitting pixels use a secondsignal line.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of an illustrative display in accordance with anembodiment.

FIG. 2 is a diagram of an illustrative pixel circuit for a displayhaving pixels with light-emitting diodes in accordance with anembodiment.

FIG. 3 is an illustrative light sensor circuit in accordance with anembodiment.

FIG. 4 is a timing diagram showing illustrative signals involved inoperating the circuitry of FIG. 3 in accordance with an embodiment.

FIG. 5 is a circuit diagram of another illustrative light sensor circuitin accordance with an embodiment.

FIG. 6 is a timing diagram showing illustrative signals involved inoperating the circuitry of FIG. 5 in accordance with an embodiment.

FIGS. 7, 8, and 9 are diagrams of illustrative layouts forlight-emitting pixels and light sensing pixels in a display inaccordance with an embodiment.

FIG. 10 is a diagram showing how interleaved light emitters and lightdetectors may be provided in a border region of a display using separatesignal lines for sensing and driving in accordance with an embodiment.

FIG. 11 is a diagram showing how interleaved light emitters and lightdetectors may be provided in a border region of a display using a sharedsignal line for sensing and driving in accordance with an embodiment.

FIG. 12 is a timing diagram illustrating signals involved in operatingthe circuitry of FIG. 11 in accordance with an embodiment.

FIG. 13 is a diagram showing how a border region of a display in anelectronic device may have an optical sensor that detects localfrustration of total internal reflection using an array of border regionlight-sensing pixels in accordance with an embodiment.

DETAILED DESCRIPTION

An electronic device such as a cellular telephone, tablet computer,wristwatch, laptop computer, desktop computer, or other electronicdevice may have a display such as illustrative display 14 of FIG. 1. Insome configurations, display 14 may cover some or all of the frontsurface of the electronic device.

As shown in FIG. 1, display 14 may have one or more layers such assubstrate 24. Layers such as substrate 24 may be formed from insulatingmaterials such as glass, plastic, ceramic, and/or other dielectrics.Substrate 24 may be rectangular or may have other shapes. Rigidsubstrate material (e.g., glass) or flexible substrate material (e.g., aflexible sheet of polymer such as a layer of polyimide or othermaterials) may be used in forming substrate 24.

Display 14 may have an array of pixels 22. Pixels 22 may, as an example,be formed from thin-film circuitry such as organic light-emitting diodethin-film circuitry.

Some of pixels 22 emit visible light that creates an image for viewingby a user of display 14 and the device containing display 14. Thesepixels may be located, for example, in a central active area (AA) ofdisplay 14. Other pixels 22 may be used for optical sensing and do notemit image light. Pixels 22 that are used in optical sensing may, in anillustrative configuration, be located along one or more edges ofdisplay 14 (e.g., in a border region that covers some or all of theperipheral edge area of display 14 along left edge L, right edge R, topedge T, and/or lower edge B). Configurations in which optical sensingcircuitry is provided along the left edge (and, if desired, the rightedge) of display 14 may sometimes be described herein as an example.

The optical sensing circuitry of display 14 may have light-sensingpixels for sensing light (e.g., for sensing the magnitude and locationof incoming light). The light-sensing pixels may sense visible light,infrared light, and/or ultraviolet light. Some light-emitting pixels indisplay 14 and/or other light sources in an electronic device mayinclude lasers or light-emitting diodes that emit visible, infrared,and/or ultraviolet light that is used in illuminating a user's fingersor other external objects. Emitted light that has illuminated the user'sfingers and that has reflected and/or scattered back towards thelight-sensing pixels may provide information about the location of theuser's fingers and/or other information (e.g., health information suchas heart rate information, fingerprint information, handprintinformation, and/or other biometric information).

The user's fingers can be detected using this type of optical sensingarrangement when the user's fingers touch display 14 (e.g., opticalsensing may be used to implement an optical touch sensor for afixed-position edge button, an edge button with a movable slider, othertouch sensitive icons and buttons on the edge of display 14, etc.)and/or when the user's fingers are in close proximity to display 14(e.g., optical sensing may be used to implement an optical proximitysensor, an air gesture sensor, a proximity-sensitive edge button, etc.).Configurations in which optical sensing is used to form an optical touchsensor in one or more border regions of display 14 that are free ofpixels that emit image light are sometimes described herein as anexample. Other portions of display 14 (e.g., the central active area ofdisplay 14 that does not include optical sensing circuitry) may beprovided with capacitive touch sensing (e.g., a two-dimensionalcapacitive touch sensor) or other non-optical touch sensor circuitry.

In some configurations, a two-dimensional capacitive touch sensor haselectrodes that overlap the active area and that do not overlap anyportion of the border region. In the border region, touch input can begathered using the optical sensor (which, in some embodiments, does notoverlap any portion of the active area). Accordingly, the active areacan use the capacitive touch sensor to gather touch input, whereas theborder region can use the optical sensor to gather touch input. In thisway, most or all of the area of display 14 can be touch sensitive, evenin arrangements in which it may be challenging to provide capacitivetouch sensing along the borders of display 14.

The pixels 22 in display 14 (e.g., the light-emitting pixels andlight-sensing pixels) may be formed in rows and columns on substrate 24.There may be any suitable number of rows and columns in the array ofpixels 22 (e.g., ten or more, one hundred or more, or one thousand ormore).

Display 14 may include display control circuitry 20. The display controlcircuitry may include display driver circuitry for controlling thelight-emitting pixels (e.g., so that the light-emitting pixels in theactive area display a desired image). The display control circuitry mayalso include optical sensor control circuitry for operating the opticalsensing circuitry of display 14 (e.g., light-sensing pixels and optionallight-emitting pixels in the sensing circuitry). Control circuitry 20may include on or more integrated circuits and, if desired, may includethin-film circuitry on substrate 24. Control circuitry 20 may be locatedat one or both ends of display 14 (see, e.g., illustrative circuitry 16along the top edge T of display 14) and/or may be located along one orboth of edges L and R (see, e.g., circuitry 18).

Signal lines on display 14 may be used for distributing power supplysignals, data, control signals, and/or other signals for the operationof display 14. Some signal paths may convey signals globally to most orall of pixels 22. For example, display 14 may have a global ground pathand other global power supply paths. Other signal paths may beassociated with particular rows and may be associated with particularcolumns of pixels 22. The signal paths for display 14 may, for example,include signal lines that extend vertically (see, e.g., paths 26, eachof which is associated with a respective column of pixels 22 and maycontain one or more vertically extending lines for that column of pixels22) and horizontally (see, e.g., paths 28, each of which extendsorthogonally to paths 26 and each of which may contain one or morehorizontally extending lines associated with a respective row ofpixels).

Circuitry 20 may be coupled to control circuitry in an electronic devicein which display 14 is mounted using paths such as path 25. Path 25 maybe formed from traces on a flexible printed circuit or other signallines. The control circuitry may be located on a main logic board in anelectronic device such as a cellular telephone, wristwatch, computer, orother electronic equipment in which display 14 is being used. Duringoperation, the control circuitry of the electronic device may supplydisplay control circuitry 20 with information on images to be displayedon display 14 and may use display control circuitry gather sensorreadings from the optical sensor circuitry in display 14. To display theimages on pixels 22, display driver circuitry in circuitry 20 may supplyimage data to data lines (e.g., data lines in paths 26) while issuingclock signals and other control signals (sometimes referred to ashorizontal control signals, emission control signals, scan signal, gateline signals, etc.) that are conveyed to display 14 over paths 28.

The light-emitting pixels of display 14 (whether active area pixels thatdisplay images or border pixels that are used to generating infraredlight or other light for use in an optical sensor), may includelight-emitting devices such as light-emitting diodes or lasers. Thelight-emitting diodes may be crystalline semiconductor light-emittingdies or thin-film light-emitting diodes. Configurations in which thelight-emitting pixels of display 14 are thin-film organic light-emittingdiodes are described herein as an example.

A schematic diagram of an illustrative pixel circuit for a thin-filmorganic light-emitting diode pixel is shown in FIG. 2. As shown in FIG.2, light-emitting pixel 22E may include light-emitting diode 38. Apositive power supply voltage may be supplied to positive power supplyterminal 34 through p-type field-effect transistor (PFET) 32 a and aground power supply voltage may be supplied to ground power supplyterminal 36. PFET 32 a is conducting when signal PEN is LOW. Diode 38has an anode (terminal AN) and a cathode (terminal CD). Transistor 32forms a constant current source with capacitor Cst, which sets thegate-to-source voltage VGS of transistor 32. The voltage across Cstcontrols the amount of current through transistor 32 and thus diode 38and therefore the amount of emitted light 40 from light-emitting pixel22E. The wavelength of emitted light 40 is determined by the structureof diode 38 and may be, as an example, visible light (e.g., red light,green light, blue light, etc.), infrared light, or ultraviolet light.For example, in the active area of display 14 that displays images,pixels such as pixel 22E may be configured to emit visible light (e.g.,red pixels may emit red light, green pixels may emit green light, andblue pixels may emit blue light). In the border region of display 14,pixels 22E may be used to emit infrared light (as an example). Infraredlight is not visible to the human eye and therefore will not disturbusers of display 14 during optical sensing operations (e.g., the emittedinfrared light will not interfere with the visible-light image presentedin the active area of display 14). Configurations in which pixels 22Eemit visible light in optical sensing regions of display 14 may also beused. For example, the border region of display 14 may include visiblelight-emitting pixels that help illuminate a user's finger or otherexternal object for optical sensing, but that do not emit visible lightthat forms part of an image. In some arrangements, ambient light and/orstray light from the active area of display 14 may help illuminate auser's fingers or other external objects that are sensed bylight-sensing pixels in display 14.

In light-emitting pixel 22E of FIG. 2, cathode CD of diode 38 is coupledto ground terminal 36, so cathode terminal CD of diode 38 may sometimesbe referred to as the ground terminal for diode 38. Cathode CD may beshared among multiple diodes (i.e., the cathodes CD of multiple diodesmay be tied to a shared voltage). The voltage on the anode AN of eachdiode is independently controlled to control the amount of light thediode produces for the pixel associated with that diode.

To ensure that transistor 32 is held in a desired state betweensuccessive frames of data, pixel 22E may include a storage capacitorsuch as storage capacitor Cst. The voltage on storage capacitor Cst isapplied to the gate of transistor 32 at node A relative to the source oftransistor 32 at node AN to control the amount of current throughtransistor 32. Data can be loaded into storage capacitor Cst using oneor more switching transistors such as switching transistor 30 andtransistor 30 a. When switching transistors 30 and 30 a are off, paths26 a and 26 are isolated from storage capacitor Cst and the differencein voltage between gate line 26 a and source line 26 is equal to thevoltage stored across storage capacitor Cst (i.e., the data value fromthe previous frame of display data being displayed on display 14). Whensignal PEN is LOW, transistor 32 a turns on, causing the current sourceformed from transistor 32 and capacitor Cst to turn on and injectcurrent into light-emitting diode 38, which emits light 40 at a levelrelated to the amount of voltage stored in Cst.

When a control signal on path 28 in the row associated with pixel 22E isasserted, switching transistors 30 and 30 a will be turned on and a newdata signal on paths 26 and 26 a will be loaded into storage capacitorCst. The new signal on capacitor Cst is applied to the gate oftransistor 32 at node A relative to the source of transistor 32 at nodeAN, thereby adjusting the current through transistor 32 and adjustingthe corresponding amount of light 40 that is emitted by light-emittingdiode 38. If desired, the circuitry for controlling the operation oflight-emitting diodes for pixels in display 14 (e.g., thin-filmtransistors, capacitors, etc. in pixel circuits such as the pixelcircuit of FIG. 2) may be formed using other configurations (e.g.,configurations that include circuitry for compensating for thresholdvoltage variations in drive transistor 32, configurations in which pixel22E has emission control transistors, reset transistors, two or morecapacitors, three or more transistors, and/or other circuitry). Thepixel circuit of FIG. 2 is merely an illustrative example of alight-emitting pixel for display 14.

FIG. 3 is a circuit diagram of an illustrative light-sensing pixel 22D.Pixel 22D has a photodetector such as photodiode 52 for detecting light50 during optical sensing. Light 50 may, for example, be infrared light,visible light, or ultraviolet light that has reflected/scattered from auser's finger or other external object. This light may be ambient lightthat has reflected/scattered towards pixel 22D from a user's finger orother object and/or may be light that was emitted from nearby (e.g.,adjacent) light-emitting pixels 22E before being reflected/scatteredtowards pixel 22D from a user's finger or other object.

Photodiode 52 may have an anode coupled to ground 54 and a cathode(which may be shared with cathode CD of pixels 22E) coupled to node N.Capacitor Cpix may be coupled between ground 54 and node N. Rowselection switch RS may be controlled by control signals (e.g., a gateline signal) on path 28. The optical sensor in the border region ofdisplay 14 may have multiple rows of pixels 22D that extend in a columnalong the length of the border region. Pixels 22D may be coupled to path26, which is used in carrying measured light signals to controlcircuitry 20. Control circuitry 20 may have sensing circuitry 60 (e.g.,correlated double sampling sample-and-hold circuitry) for receiving andprocessing signals from the photodiodes in pixels 22D.

Sensing circuitry 60 may have a sense amplifier formed from amplifier 56and associated feedback capacitor CFB. Reset switch INTRST may becoupled between the output of amplifier 56 and its negative input.Amplifier 56 may receive bias voltage Vbias at its positive input. Theoutput of each light-sensing pixel 22D may be received via row selectionswitch RS at the negative input of amplifier 56. The sample-and-holdcircuitry for capturing and digitizing the output Vout of amplifier 56may include first sample-and-hold switch CDS1 and second sample-and-holdswitch CDS2. When switch CDS1 is closed, Vout may be sampled tosample-and-hold capacitor C1. When switch CDS2 is closed, Vout may besampled to sample-and-hold capacitor C2. Switching circuitry andanalog-to-digital control circuitry (ADC) may be used to digitize thevoltages gathered using the sample-and-hold circuits. Signalmeasurements (e.g., light measurements gathered using sensing circuitry60) may be processed by control circuitry to detect finger touch inputand other user input.

During sensing with light-sensing pixel 22D, sensing circuitry 60samples the voltage from pixel 22D before and after capacitor Cpix ofpixel 22D gathers charge associated with incoming light 50. The amountof charge gathered on capacitor Cpix is proportional to the amount oflight 50 that is received in a given measurement interval, so bymeasuring the output of pixels 22D (e.g., the charge on capacitor Cpix),the amount of detected light 50 during each measurement interval can bemeasured.

FIG. 4 is a timing diagram of signals involved in operating a displaywith pixels such as light-sensing pixels 22D of FIG. 3. During timeperiod TI, row selection switch RS is open, light 50 is being receivedby pixel 22D, and this received light is creating current through diode52 that is stored in capacitor Cpix. This amount of stored charge ismeasured using sensing circuitry 60 by opening and closing the switchesof FIG. 3 in accordance with the timing diagram of FIG. 4. During timeperiod T1, sense amplifier reset switch INTRST is closed while rowselect switch RS is open. The sense amplifier tries to equilibrate itsinputs, so that voltage Vbias is driven onto node N. During period T2,switch CDS1 is closed to gather a first sample of output voltage Vout.Switch CDS1 remains closed until a certain time after INTRST is openedto ensure that the KT/C noise from CFB is captured. During period T3,row select switch RS is closed to transfer the stored charge fromcapacitor Cpix to sensing circuitry 60. This causes Vout to rise. Therise in Vout due to the closing of switch RS is proportional to thechange in voltage at node N (ΔVpix, which is proportional to the amountof received light 50 during period TI) times Cpix divided by CFB. Duringperiod T4, switch CDS2 is closed to sample Vout after this change involtage has occurred. Control circuitry can then process the measureddifference between the two sampled values of Vout to determine themagnitude of light 50 and thereby determine if a finger is present onthe optical sensor, whether a finger is in close proximity to theoptical sensor, etc.

Another illustrative light-sensing pixel circuit is shown in FIG. 5.Illustrative control signals for operating light-sensing pixel 22D ofFIG. 5 are shown in FIG. 6. This type of circuit may provide completeisolation of sense node N from the input to the sensing circuitry(coupled to the end of path 26) and can be used to perform doublesampling. Low assertion of signal RST causes photodiode 52 and CPIX tobe reset to VBIAS. Integration of photocurrent through photodiode 52into CPIX commences after RST signal is deasserted. Transistor 51 is asource follower buffering the pixel voltage Vpix across Cpix. Uponassertion of signal RS, the buffered pixel voltage is connected to thesense node. The voltage mode buffer of FIG. 5 buffers the voltage andthis buffered voltage is passed on to a sample-and-hold circuit (seeCDS1 and CDS2 of FIG. 3). The integration time is the time betweendeassertion of signal RST and the assertion of signal RS. Other type ofcircuits can be used for light-sensing pixels 22D, if desired. Theexamples of FIGS. 3 and 5 are illustrative.

FIGS. 7, 8, and 9 show illustrative layouts for light-emitting pixels22E and light sensing pixels 22D in display 14. Light-emitting pixels22E in active area AA may include colored pixels (e.g., visible lightpixels such as red, green, and blue pixels) for displaying coloredimages in active area AA. Images are not displayed in border region B.Border region B runs along the peripheral edge of display 14 and maycontain one or more rows and/or columns of light-sensing and/orlight-emitting pixels. In the example of FIG. 7, border region B haslight-emitting pixels 22E (which may, if desired, emit visible,infrared, and/or ultraviolet light) and light-sensing pixels 22D (whichmay detect the emitted light after the emitted light has reflectedand/or scattered from a user's fingers or other external objects). Usingthe optical sensor formed from pixels 22D and pixels 22E in borderregion B, display 14 may gather touch input (e.g., finger input) inborder region B. To gather touch input seamlessly across display 14,display 14 may also have a two-dimensional touch sensor in active areaAA. As an example, display 14 may have a two-dimensional capacitivetouch sensor that overlaps active area AA, but that does not overlap anyof border region B (see, e.g., the illustrative two-dimensional array ofcapacitive touch sensor electrodes 70 overlapping pixels 22E in activearea AA and corresponding capacitive touch sensor processing circuitry72).

In the example of FIG. 7, the optical sensing circuitry in border regionB contains light-emitting pixels 22E and light-sensing pixels 22D thatalternate along the length of elongated border region B (e.g., infraredlight-emitting pixels and infrared light-sensing pixels are present inalternating rows of display 14). In the example of FIG. 8, border regionB contains only a column of light-sensing pixels 22D (e.g., fordetecting infrared light and/or visible light or ultraviolet light).Ambient light and/or light from nearby active area visible-light pixels22E may be used to illuminate a user's fingers or other external objectsduring optical sensing with pixels 22D. In the example of FIG. 9, borderregion B contains a single column of light-emitting pixels 22E (e.g.,infrared light-emitting pixels) and a single corresponding column oflight-sensing pixels (e.g., infrared light-sensing pixels) 22D.

In these illustrative arrangements, border region B contains opticalsensing circuitry that with a line of pixels (e.g., a column of pixels)that can serve as a one-dimensional (linear) optical sensor (e.g., aone-dimensional optical touch sensor or one-dimensional opticalproximity sensor). Configurations in which border region B containsmultiple lines (e.g., columns) of light-sensing pixels, containsmultiple lines (e.g., columns) of alternating light-sensing andlight-emitting pixels, and/or contains multiple lines (e.g., columns) oflight-sensing pixels and multiple lines (e.g., columns) of lightemitting pixels to create a two-dimensional optical sensor in borderregion B may also be used.

FIG. 10 is a diagram showing how row-interleaved light-emitting pixelsand light-sensing pixels in border region B may each have a respectivevertical signal line in path 26. Pixels 22D extend along a first line(e.g., column) that runs along the length of border region B and pixels22E extend along a parallel second line (e.g., column) that runs alongthe length of border region B. For example, each column of pixels22E/22D such as the illustrative column of pixels in border region B ofFIG. 10 may have a first line that is used as a data line for loadingdata into pixels 22E or for otherwise driving pixels 22E and a secondline that is separate from the first line that is used as a sense linefor gathering photodiode signals (sensed light signals) from pixels 22D.

FIG. 11 is a diagram showing how row-interleaved light-emitting pixelsand light-sensing pixels in border region B may share a common verticalsignal line in path 26. For example, each column of pixels 22E/22D suchas the illustrative column of pixels in border region B of FIG. 11 mayhave signal line that is partly used for loading data into pixels 22E orfor otherwise driving pixels 22E and that is partly used as a sense linefor gathering photodiode signals (sensed light signals) from pixels 22D.

In the example of FIG. 11, switches Φ1 and Φ2 control whether driver 82is used in driving signals to light-emitting pixels 22E (when switch Φ1is closed to couple pixel driver circuit 82 to path 26 and switch Φ2 isopen to isolate sensing circuitry 84 from path 26) or whether senseamplifier 84 is receiving light measurements carried over path 26 fromlight-sensing pixels 22D (when switch Φ1 is opened to isolate pixeldriver circuit 82 from path 26 and switch Φ2 is closed to couple theinput of sensing circuitry 84 to path 26). As shown in the timingdiagram of FIG. 12, during operations 86, when switch Φ1 is closed,switches Φ11, Φ12, Φ13, etc. are closed in sequence to select successiverows of light-emitting pixels 22E to drive with driver 82. Duringoperations 88, when switch Φ2 is closed, switches Φ21, Φ22, Φ23, etc.are closed in sequence to select successive rows of light-sensing pixels22D to couple to the input of sensing circuitry 84. Other timingsequences for switches Φ1, Φ11, Φ12, Φ13, Φ2, Φ21, Φ22 and Φ23 arepossible. For example, switches Φ21, Φ11, Φ22, Φ12, Φ23 and Φ13 may beengaged one at a time and in sequence, with appropriate assertion ofswitches Φ1 and Φ2 (e.g. Φ2, Φ1, Φ2, Φ1, Φ2, Φ1, respectively).

In the example of FIG. 12, the optical sensing circuitry in elongatedborder region B contains light-sensing pixels 22D arranged along thelength of border region B (e.g., infrared light-detecting pixels formedfrom infrared photodiodes or other infrared photodetectors and/orvisible light-detecting pixels that are formed from visible photodiodesor other visible photodetectors. Light-emitting device 100 (e.g., alight-emitting diode or laser diode configured to emit light at aninfrared and/or visible light wavelength) may emit light 102 into anadjacent edge 104 of a transparent member such as display cover layer106. Display cover layer 106 may be formed from a transparent materialsuch as glass, clear polymer, sapphire or other crystalline material,other transparent materials, and/or combinations of these materials andmay overlap all of the pixels in display 14. Display cover layer 106may, as an example, have a rectangular shape or other shape that overlapthe pixels in active area AA and that extends over border areas such asborder region B of FIG. 13.

Light 102 that is emitted from light-emitting device 100 may be guidedbetween the upper and lower surface of display cover layer 106 along thelength of border region B in accordance with the principal of totalinternal reflection. In the absence of external objects such as userfinger 108, light 102 does not penetrate into the interior of theelectronic device in which display 14 is mounted (e.g., light 102 doesnot reach any of the overlapped light-sensing pixels 22D). At a locationof the display cover layer 106 where the surface of layer 106 is touchedby finger 108 or external external object, total internal reflectionwill be locally defeated. This will cause light 102 to exit outwardlyfrom display cover layer 106, where light 102 will strike finger 108 andbe scattered back downwards by finger 108 as scattered light 102′. Thelocation where scattered light 102′ is present may be detected byanalyzing the output of light-sensing pixels 22D (e.g., by detecting theelevated output of the light-sensing pixel 22D at the location wherefinger 108 scattered light 102′ inwardly). In this way, the location offinger 108 along dimension Y (e.g., along the length of the borderregion B of display 14) may be measured. With configurations of the typeshown in FIG. 13, there may be one or more parallel columns oflight-sensing pixels 22D running along the length of border region B.Additional columns of pixels 22D may, as an example, be included toprovide additional location information (e.g., location along dimensionX in the example of FIG. 13 in addition to location along dimension Y).

Display 14 may be operated in a system that uses personally identifiableinformation. It is well understood that the use of personallyidentifiable information should follow privacy policies and practicesthat are generally recognized as meeting or exceeding industry orgovernmental requirements for maintaining the privacy of users. Inparticular, personally identifiable information data should be managedand handled so as to minimize risks of unintentional or unauthorizedaccess or use, and the nature of authorized use should be clearlyindicated to users.

The foregoing is merely illustrative and various modifications can bemade by those skilled in the art without departing from the scope andspirit of the described embodiments. The foregoing embodiments may beimplemented individually or in any combination.

Table of Reference Numerals 14 display 16, 18, 20 display controlcircuitry 25, 26, 26a, 28 paths 24 substrate 22 pixels L, R, T, B edges30, 32, 32a, transistors Cst capacitor 30a, 51 A, B nodes AN anode CDcathode 38 light-emitting diode 40 light 34, 36 terminals 22Dlight-sensing RS, INTRST, switches pixel CDS1, CDS2 N node 52 photodiode50 light 60 sensing circuitry 56 amplifier CFB capacitor C1, C2capacitors Cpix capacitor 70 electrodes 72 touch sensor processingcircuitry B border region AA active area 82 driver 84 sensing circuitry86, 88 operations 100 light-emitting device 102, 102′ light 108 finger106 display cover 104 edge layer

What is claimed is:
 1. A display having an active area and a border region that runs along a peripheral edge of the active area, comprising: an array of light-emitting pixels on a substrate, wherein the array of light-emitting pixels is configured to display an image in the active area and wherein the active area does not contain light detectors; and an optical sensor on the substrate in the border region that includes light-sensing pixels configured to measure light.
 2. The display defined in claim 1 further comprising a capacitive touch sensor that overlaps the active area.
 3. The display defined in claim 1 wherein the optical sensor comprises an infrared optical sensor.
 4. The display defined in claim 1 wherein the optical sensor comprises a plurality of light-emitting pixels.
 5. The display defined in claim 1 wherein the light-sensing pixels comprise infrared light-sensing pixels.
 6. The display defined in claim 1 wherein the light-sensing pixels comprise infrared light-sensing pixels and wherein the optical sensor further comprises infrared light-emitting pixels.
 7. The display defined in claim 6 wherein the infrared light-sensing pixels and the infrared light-emitting pixels are arranged in two parallel lines extending along the border region.
 8. The display defined in claim 6 wherein the infrared light-sensing pixels and the infrared light-emitting pixels alternate with each other along the border region.
 9. The display defined in claim 6 wherein the border region is free of light-emitting pixels and the light-emitting pixels of the array contain only visible light-emitting pixels.
 10. The display defined in claim 1 wherein the optical sensor in the border region forms an optical touch sensor configured to detect touch input and wherein the display further comprises a non-optical two-dimensional touch sensor in the active area that is configured to detect touch input.
 11. The display defined in claim 10 wherein the light-sensing pixels comprise infrared light-sensing pixels and wherein the non-optical two-dimensional touch sensor comprises a two-dimensional capacitive touch sensor that overlaps the active area and that does not overlap the border region.
 12. A display, comprising: active area pixels configured to display an image in an active area that is free of light sensing circuitry; and an optical sensor that has infrared light-emitting pixels and infrared light-sensing pixels, wherein the optical sensor is in a border region that runs along a peripheral edge of the active area.
 13. The display defined in claim 12 further comprising: a substrate layer, wherein the active area pixels comprise thin-film visible-light-emitting pixels on the substrate layer in the active area.
 14. The display defined in claim 13 wherein the infrared light-sensing pixels comprise thin-film infrared light-sensing pixels on the substrate layer in the border region.
 15. The display defined in claim 14 wherein the infrared light-emitting pixels comprise thin-film infrared light-emitting pixels on the substrate layer in the border region.
 16. The display defined in claim 15 further comprising capacitive touch sensor electrodes that overlap the active area, wherein no capacitive touch sensor electrodes overlap the border region.
 17. A display, comprising: active area pixels on a substrate that are configured to display an image in an active area that is free of light sensing circuitry; and an optical sensor in a border region of the substrate that runs along a peripheral edge of the active area, wherein the border region does not have pixels that display images and wherein the optical sensor comprises light-sensing pixels that extend along the border region.
 18. The display defined in claim 17 further comprising capacitive touch sensor circuitry overlapping the active area, wherein the border region is not overlapped by any capacitive touch sensor circuitry.
 19. The display defined in claim 18 wherein the light-sensing pixels comprise infrared light-sensing pixels and wherein the optical sensor comprises infrared light-emitting pixels.
 20. The display defined in claim 19 wherein the border region contains a signal line that is configured to supply signals to the infrared light-emitting pixels and that is configured to carry signals from the infrared light-sensing pixels.
 21. The display defined in claim 19 wherein the border region contains a first signal line that is configured to supply signals to the infrared light-emitting pixels and a second signal line that is configured to carry signals from the infrared light-sensing pixels.
 22. The display defined in claim 17 further comprising a transparent display cover layer that overlaps the active area and the border region, the optical sensor further comprising a light-emitting device that is configured to emit light into an edge of the transparent display cover layer that is guided by total internal reflection along the border region until total internal reflection is locally defeated by an external object on a surface of the display cover layer, thereby scattering light through the display cover layer towards the light-sensing pixels and wherein the optical sensor is configured to measure a location of the external object on the surface using output from the light-sensing pixels that extend along the border region.
 23. The display defined in claim 22 wherein the light-emitting device is an infrared light-emitting device. 